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BRS YEAR 2 > Neuro - Auditory System > Flashcards

Neuro - Auditory System Flashcards

1
Q

What are the 3 parts of the ear?

A

Outer
Middle
Inner

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2
Q

Where is the ear organ located?

A

In the petrous part of the temporal bone - the hardest bone in the body

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3
Q

What makes up the outer ear

A

The pinna and the ear canal

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4
Q

What are the functions of the outer ear

A

Capture sound and focus it on the tympanic membrane
Amplify some frequencies by resonance in the canal
Protect the ear from external threats

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5
Q

How does the outer ear protect from external threats

A

Hairs in the canal

Wax provides physical barrier and also pH of wax kills things coming into the ear

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6
Q

What is the function of the middle ear

A

Amplification of sound

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7
Q

What makes up the middle ear

A

Tympanic membrane

3 ossicles with their associated muscles, tendons and ligaments

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8
Q

How does the middle ear amplify sound

A

Focuses vibrations from large surface area onto the smaller oval window to increase pressure
Uses leverage from the incus-stapes joint to increase the force on the oval window

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9
Q

What makes up the inner ear

A

Cochlea

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10
Q

What is the function of the inner ear

A

transduce vibrations into nervous impulses and also provide a frequency and intensity analysis of sound

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11
Q

What are the 3 cochlea compartments

A

Scala vestibuli
Scala media
Scala tympani

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12
Q

What is perilymph

A

Fluid found in the scala vestibuli and tympani which is high in sodium

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13
Q

What is endolymph

A

Fluid found in the scala media high in potassium

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14
Q

Where is the organ of Corti located

A

In the basilar membrane of the scala media

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15
Q

How is the Basilar membrane organised

A

Tonotopically - there s a narrow and tight base with a wide and loose apex

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16
Q

What frequencies cause vibrations in the base of the Basilar membrane

A

High frequency

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17
Q

What frequencies cause vibrations in the apex of the basilar membrane

A

Low frequency

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18
Q

What makes up the organ of Corti

A

Thousands of hair cells (both IHC and OHC)

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19
Q

What is the tectorial membrane

A

Located above the hair cells and allow deflection of hair cells to cause cell depolarisation

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20
Q

What cells are in constant contact with the organ of Corti

A

OHC

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21
Q

What nerves do IHC mainly carry

A

95% afferent fibres of the auditory nerve

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22
Q

What nerves do OHC mainly carry

A

95% efferent fibres of the auditory nerve

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23
Q

What is the function of afferent auditory nerves

A

Transduction of sound into nerve impulses

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24
Q

What is the function of efferent auditory nerves

A

Modulation of the sensitivity of the response (active amplifying of the OHC)

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25
Q

What are the hairs of hair cells called

A

Stereocilia

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26
Q

What does stereocilia deflection lead to

A

Deflection towards the longest cilium causes the opening of K channels and thus depolarisation

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27
Q

Explain the process of transduction

A

Vibrations cause the IHC to contact the tectorial membrane and thus their stereo cilia deflect and K channels are opened. There is influx of K into the cell and thus depolarisation, leading to the opening of voltage gated calcium channels.
These channels open and therefore calcium causes the exocytosis of glutamate out of the fair cells and thus a nervous response in propagated through the afferents of the auditory nerve

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28
Q

Describe the pathway of auditory information from the cochlea to the cerebral hemisphere

A

Spiral ganglions from the cochlea extend to the cochlear nucleus.
Auditory information then reaches the superior olive and crosses contralaterally (some fibres stay ipsilateral).
Fibres then travel to the inferior colliculus in the brainstem and then to the medial geniculate body in the thalamus. Finally fibres reach the auditory cortex in the cerebral hemisphere.

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29
Q

What is the need for tonotopic arrangement of hearing

A

If we can’t discriminate different frequencies then we cannot discriminate or interpret speech

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30
Q

What is frequency

A

Cycles per second, perceived tone

Pitch

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31
Q

What is amplitude

A

Sound pressure, subjective attribute correlated with physical strength (loudness)

32
Q

What is the range of frequency for hearing

A

20-20,000 Hz

33
Q

What is active amplifying

A

OHC can contract or elongate to alter whether or not IHC will come into contact with the tectorial membrane - this means that we can hear sounds that are too soft and our ears aren’t damaged from sounds that are too loud

34
Q

What is the normal range of amplitude

A

0-120dB

35
Q

What type of scale is the decibel scale

A

Log scale

36
Q

What is the need for a log scale for decibels

A

Allows us to compress the scale on a graph - reflects the fact that many physiological processes are non linear

37
Q

How does hearing alter with age

A

Hearing acuity decreases with age, particularly higher frequencies - medium and low can be affected with the progression of a hearing loss

38
Q

What are the 3 questions in a hearing assessment?

A

Is there hearing loss?§
If so - of what degree?
Of what type?

39
Q

What procedures can we use to test hearing

A 
Tuning fork 
Audiometry
Central processing assessment 
Tympanometry
Otoacoustic emission
Electrocohcleography 
Evoked potentials
40
Q

What is a tuning fork used for

A

Establish probable presence or absence of a hearing loss with a significant conductive component, therefore provide early and general information if audiometry is not available

41
Q

What is a Weber test

A

Vibrate fork to see if patent hears on both sides the same

42
Q

What is a Rinne test

A

Directly stimulate the bone as endolymph vibrates to see if there is a problem with the middle/ inner ear

43
Q

What is pure tone audiometry (PTA)

A

Science of measuring hearing acuity for variations in sound intensity and frequency

44
Q

What does an audiometer do

A

The device used to produce sound of varying intensity and frequency

45
Q

What is an audiogram

A

Where the hearing thresholds are listed to define if there is a hearing loss or not

46
Q

What is a normal hearing threshold for an audiogram

A

0-20dB

47
Q

What is central processing assessment

A

Assessment of hearing abilities rather than just tone detection

48
Q

What are examples of central processing assessment

A

Sound localisation
Filtered speech
Speech in noise

49
Q

What is tympanometry

A

Examination used to test the condition of the middle ear and mobility of the tympanic membrane and the conduction bones by creating variations of air pressure in the ear canal

50
Q

What is A in tympanometry

A

Normal

51
Q

What is C in tympanometry

A

Negative middle ear pressure

52
Q

What can be the causes of B in tympanometry

A

Middle ear effusion
Perforation of the tympanic membrane
Eustachian (pharyngotympanic) tube dysfunction
Occluded ear canal

53
Q

What are otoacoustic emissions

A

Sounds produces by the normal cochlea, by the OHC as they expand and contract

54
Q

When are OAEs performed

A

Newborn hearing screening and hearing loss monitoring

55
Q

What is an auditory brainstem response

A

Electrical responses from the auditory pathway evoked by clicks (auditory evoked potential)

56
Q

When are ABRs used

A

More commonly used in clinic and doesn’t require attention from the patient - alterations in latency of waves can point to the location of a deficit.
Commonly used in babies and children

57
Q

What affects cortical potentials

A

Cortical potentials could be affected in neurological conditions or processing problems

58
Q

What is conductive hearing loss

A

Problem is located in the outer or middle ear

59
Q

What is sensorineural hearing loss

A

Problem is located in the inner ear or the auditory nerve

60
Q

What is mixed hearing loss

A

Conduction and transduction of sound are affected therefore the problem stems from multiple parts of the ear

61
Q

What do we see in an audiogram for conductive hearing loss

A

Bone conduction normal but air conduction shows hearing loss

62
Q

What do we see in an audiogram for sensorineural hearing loss

A

bone and air conduction are both affected equally

63
Q

What do we see in an audiogram for mixed hearing loss

A

Bone and air conduction are both affected but not equally

64
Q

What are the classifications of hearing loss

A

Mild, moderate, severe, profound

65
Q

What are causes of outer ear hearing loss

A

Wax

Foreign body

66
Q

What are causes of middle ear hearing loss

A

Otitis

Otosclerosis

67
Q

What are causes of inner ear hearing loss

A

Presbycusis

Ototoxicity

68
Q

What are causes of nerve hearing loss

A

VIII nerve tumour

69
Q

What are the 4 domains of hearing loss treatment

A

Underlying cause
Hearing aid
Cochlear implant
Brainstem implant

70
Q

What are hearing aids

A

Hearing aids amplify sound but do not replace any structure

71
Q

What do we need to have a hearing aid

A

Functioning hair cells

72
Q

What is a cochlear implant

A

Replaces the function of hair cells by receiving sound analysing it, transforming it into electrical signals and sending an electric impulse directly to the auditory nerve

73
Q

What do we need to have a cochlear implant

A

Functional auditory nerve

74
Q

What is a brainstem implant

A

When the auditory nerve is affected, electrical signal can be sent to a set of electrodes places directly into the brainstem

75
Q

When is a brainstem implant advised

A

People with bilateral important auditory nerve damage - is a risky procedure

BRS YEAR 2 (37 decks)

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